Galactic and Anomalous Cosmic Rays in the Heliosheath

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Galactic and Anomalous Cosmic Rays in the
Heliosheath
? V-1
21st ECRS, Košice, September 2008
? V-2

• József K?ta
• University of Arizona
• Tucson, AZ 85721-0092, USA
• Thanks to J.R. Jokipii, J. Giacalone

kota_at_lpl.arizona.edu
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Motivation where is the source?is history
repeating itself ??
ACR fluxes continued to increase beyond TS

Source outside
Shock
V. Hess 1912
Voyager-1 December 2004 Similar result from V-2
(2007)
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? Are Anomalous Cosmic Rays (ACRs) indeed
accelerated at the solar wind termination shock
(TS) ? Likely yes but ? Bluntness of TS
counts ? Topology between Shock Field lines
counts
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Heliosphere our cosmic environment
lt 1000 AU (10 lightdays) gt
Pristine ISM
? V1
TS
Solar material
Perturbed ISM
26 km/s
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Global structure of Heliosphere
VLISM partially ionized H,He 0.1/cc µG B ?
ACR
SEP
GCR
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ACRs are accelerated at the solar wind
Termination Shock Same Physics as SNR
ACRs
SNR
Diffusive Shock Acceleration 1st order Fermi
Energy gain from crossing the shock many times
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LECP Low energy charged particles (Decker
JHU-APL)
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Voyager-1 after crossing the TS
ACR fluxes continued to increase into
the Heliosheath ? Temporal variaton (Florinski
Zank,2006) ? Magnetic topology (McComas
Schwadron, K?ta Jokipii) ? Combination of the
two?
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First Signature of Blunt Shock

• Voyager-1 observed large beaming anisotropies
  seemingly from the sunward direction.
• Interpreted in terms of multiple intersection
  between the Parker spiral field and the blunt TS
• Hint for a deformation of the shock (likely due
  to interstellar B).

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How do we understand anti-sunward
anisotropies?Magnetic field line may intersect
the TS multiple times.
Jokipii, Giacalone, and Kota 2004, Kóta and
Jokipii 2004 Multiple intersection also explains
the two population spectrum
V-2
V-1
Displacement of the nose helps
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McComas and Schwadron (2006) Blunt Shock
acceleration at Flanks ?
Short time for acceleration
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Topological effects on ACR spectrum

• Acceleration ineffective at the nose due to lack
  of time fof acceleration.
• ACR spectrum does not unfold at the TS
• ACR flux continues to increase into the
  heliosheath
• Could have been anticipated

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2-D Model TS Offset Circle

• In the modeling we select an offset sphere for
  the TS
• Another possibility is bullet shape (McComas
  Schwadron, 2006)
• Nose region (V1 and V2) is similar in either case
• Differences can be expected for the tail region.
  Tail region turn effective for sphere and
  probably less effective for bullet shape.
• Consider preferential injection at flanks

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Blunt Shock (offset circle)perpendicular
diffusion included (?0.02)
Polar contours of simulated 200keV fluxes
spectrum along the TS
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2-DSimulation Blunt shock
Model 2-D plane, TS offset circle, uniform
injection at 10 keV, ?0.02
V-2
Radial variation at fixed azimuth fluxes
continue increase beyond TS
V2
V1
V-1
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Larger perpendicular diffusion ?0.05 effect
smaller but still there
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Summary
?V-1
?V-2
? Magnetic field lines cross the blunt TS
multiple times. This explains
? Upstream field-aligned anisotropies - away
from the Sun (V-1) TS offset helps - toward
the Sun (V-2) if TS is offset
? Two-population spectrum low energy particles
are accelerated at nearby fresh shock. ACRs
are accelerated farther away are still modulated
at the TS, and continue to increase into the
heliosheath. ? 2-D Shock differs from 1-D shock
(topology) Think in 2 D (at least) ? Topology
may be important at other shocks too.
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Motto

• ? Make everything as simple as possible, but not
  simpler

Topology counts
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Voyager-1 in the Heliosheath

• ? V-1 crossed the Termination Shock on December
  16, 2004

After Crossing ?small anisotropies ? small
day-to-day variability ? ACRs still modulated ?
Double power law spectra with break around few
MeV/n (HeH110)
Before Crossing ? large beaming anisotropies
from sunward direction ? large day-to-day
variability ? ACRs still modulated
two-population!?
? Voyager-2 crossed the TS on DOY 244, 2007
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Voyager -1 -2 reached the TS 2004/2007
SW Plasma
LECP
CRS
radio
Launched in 1977
B
Interestingly in the same year as the theory of
shock acceleration
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Where is the Termination Shock ?
Very different methods all predict 100 AU range
Shock is not steady but moves in response of
solar input
E.C. Stone 2001
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Uneven injection preferential injection at flanks
Injection at 10 keV, qsin(?)2
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Preferential injection at flanks contnd